Correlation between\n2D Square Ice and 3D Bulk Ice\nby Critical Crystallization Pressure

Low-dimensional ice trapped in nanocapillaries is a fascinating\nphenomenon and is ubiquitous in our daily lives. As a decisive factor\nof the confinement effect, the size of the nanocapillary significantly\naffects the critical crystallization pressure and crystalline structure,\nespecially for multilayered ices. By choosing square ice as a typical\ntwo-dimensional (2D) multilayered ice pattern and using all-atom molecular\ndynamics simulations, we further unveil the variation mechanism of\ncritical crystallization pressure with the nanocapillary size. The\nresults show a strong dependence of the critical crystallization pressure\non the size of the graphene sheet for monolayer, bilayer, and trilayer\nsquare ice. The quasi-macroscopic crystallization pressure, the actual\npressure of water molecules, and the freezable region between them\nare all strongly dependent on the nanocapillary width. As the size\nof the capillary becomes larger in all three directions, the critical\ncrystallization pressure converges to the true macroscopic crystallization\npressure, which is very close to the value of the crystallization\npressure for bulk ice. A direct correlation is established between\n2D square ice and three-dimensional (3D) bulk ice by the critical\ncrystallization pressure. There is an unfreezable threshold for crystallizing\nspontaneously in practice when the quasi-macroscopic crystallization\npressure is equal to the actual pressure, which can explain the limit\nof nanocapillary width for multilayered ice.